The Boston bombing was small and used low-grade explosives. Islamists and right-wing extremists like Timothy McVeigh use vastly more powerful explosives. So, I think this was done by yet another American lone wacko, of whom we have far too many.
Politics in the Zeros
"A republic, if you can keep it." Defeat MAGA
Politics in the Zeros
"A republic, if you can keep it." Defeat MAGA